1. Field of the Invention
The present patent application for industrial invention relates to a positive displacement gear pump.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Various types of positive displacement pumps with internal gears are known on the market, being used to transport liquid or gaseous fluids from a suction pipe to a discharge pipe of the pump.
FIG. 1 shows a positive displacement gear pump according to the prior art, generally indicated with reference numeral (101). The pump (101) comprises a casing (102) with suction pipe (I) and discharge pipe (O). Two identical rotors (103) are mounted inside the casing (102). Each rotor (103) comprises a gear composed of a toothed wheel. Each rotor comprises a plurality of linear or helicoidal teeth (130) that define a plurality of cavities (131) between said teeth (130).
The two gears (103) are engaged in such manner that the teeth (130) of one gear are engaged into the cavities (131) of the other gear, and vice versa. So the fluid enters the suction pipe (I) and comes out of the discharge pipe (O).
This type of positive displacement pumps of the prior art is impaired by drawbacks caused by fluid encapsulation. As a matter of fact, the fluid treated by the pump is trapped in the cavities of the rotor and compressed by the teeth of the other rotor, thus generating micro-explosions. Said micro-explosions considerably reduce the number of rotor revolutions, causing a considerable wear of the rotors and generating failure points in the rotor toothing.
Vane pumps are additionally known, comprising a rotor provided with cavity in which vanes slide radially. The rotor is mounted eccentrically with respect to the seat of the casing where it is housed and the vanes are stressed by springs or by the centrifugal force towards the surface of the rotor housing.
Said vane pumps permit a limited number of revolutions, cause early wear of vanes and require oil lubrication and consequently a separator to separate oil from the fluid treated by the pump.
US2011/0135525 discloses a non-eccentric motor comprising male rotors provided with protuberances and female rotors provided with cavity engaged by the protuberances of the male rotor. However, the male rotors have a particular shape of the protuberances which difficult to make, since the protuberance are obtained in a single piece with the rotor body.
The purpose of the present invention is to overcome the drawbacks of the prior art, by disclosing a positive displacement gear pump capable of avoiding fluid encapsulation.
Another purpose of the present invention is to obtain such a positive displacement gear pump that is able to operate with a high number of revolutions and is extremely reliable and safe.